This invention relates to a golf ball, and more specifically, to a golf ball with the characteristics of improved distance and improved aerodynamic symmetry. The golf ball has a dimpled surface with the dimples arranged on the surface in patterns created by a series of arcs of great circles. The patterns are such as to allow a large percentage of the surface of the ball to be covered by dimples and to maintain aerodynamic symmetry without the need for changing the depth of the dimples in the polar regions of the ball.
It has become general knowledge to those skilled in the art of making golf balls that the passage of the symmetry rule by the United States Golf Association and the Royal and Ancient has had a negative impact on the distance being able to be achieved by a golf ball. Prior to this rule, golf ball development was moving toward more and more of the ball surface being covered by dimples and having only one circumferential path around the surface of the ball which was not intersected by dimples, that being the true "equator" or seam line of the ball. Further, there was an attempt to avoid multiple parallel rows of dimples. The benefits of avoiding non-intersecting circumferential paths and parallel rows of dimples are pointed out in U.S. Pat. Nos. 4,141,559 and in U.S. Pat. No. 4,560,168. Following the teachings of these patents, further developments were made and improvements, such as those described in U.S. Pat. No. 4,729,861, were made.
With the passage of the symmetry rule, the golf ball industry suffered a substantial setback in technology. It was discovered that the golf balls of U.S. Pat. Nos. 4,141,559, 4,560,168, and 4,729,861, as well as others, failed to pass this rule, which requires that the trajectory, distance, and flight time of the golf ball be essentially the same when hit on the equator with an axis through the poles, as when hit on the equator with an axis through the equator.
Numerous attempts have been made to correct the symmetry of the golf ball to allow passage of this requirement. The most popular method of correcting symmetry has been the use of multiple parting lines or dimple-free, great circles on the ball. Numerous patents have been granted on golf balls having four, five, six, seven, and ten great circles, or circumferential pathways, which do not intersect dimples.
Another method of achieving aerodynamic symmetry was disclosed in U.S. Pat. No. 4,744,564, which described a means of reducing the volumes of polar dimples by making the dimples shallower in this area. This allowed the ball to pass symmetry, but created an area of higher aerodynamic drag in the polar region, thus inhibiting the distance the ball would travel.
U.S. Pat. No. 5,087,048 describes another means of achieving symmetry by utilizing a certain number of smaller, deeper, dimples which are located according to specific guidelines. This restricts the designer from utilizing a number of different dimple sizes and results in "clusters" of different sized dimples.